The blues, beavers, deer, the paw prints of a bear ... Max Davidson has as
much fun as Mark Twain's hero on the 'monstrous big, Mississippi'.

Dawn on the Mississippi and the only sound, apart from the drone of mosquitoes, is the strumming of a guitar in the next tent. John Ruskey, Jesus look-alike, sole proprietor of the Quapaw Canoe Company, mixer of the best margarita between Memphis and New Orleans, is singing the blues.

"... angry women... gee, they make a mess out of you..." I have to strain to hear the words, an odd mixture of melancholy, sentiment and defiance. "... got to get me another woman... you can get you another man..." This is not the United States of the cereal commercials: happy families sitting around a breakfast table. It is a bleaker, lonelier world. Relationships between the sexes are as transitory as the Mississippi itself, that great watery highway through the heart of the nation.

At a quarter to six, as the first streaks of red are starting to appear in the sky to the east, John unzips his tent and pads down to the river. "Felt so lonesome in the city," he croons, as he washes his face in the murky water. "Jus' had to get away." In the wood behind the tents, the drone of mosquitoes is supplemented by birdsong and the croak of bullfrogs. Away in the distance, a boat sounds its foghorn, a single mournful note that lingers for what seems an eternity. By half-past six, we are drinking strong black coffee, scented with chicory, around a camp fire.

John's brother Chris, a doctor from Colorado Springs, crawls out of his tent to join us, followed by his sons Nicky, eight, and Gavin, six. "Morning, Uncle John," says Nicky, wiping sleep from his eyes. "Morning, Max," croaks Gavin. Then a long, contemplative silence as four Ruskeys and a Davidson, on an all-male, back-to-nature canoeing trip, savour one of the last great wildernesses in America.

We are camped on a sandbank on an island in the middle of the river - the perfect vantage-point to enjoy what Mark Twain called "the great Mississippi, the majestic, magnificent Mississippi, rolling its mile-wide tide along". The river is only about half-a-mile wide where we are, just west of Clarksdale, but the impression of vastness is overwhelming all the same. The trees on the far bank, silhouetted against the rising sun, are just tiny black stumps, a frame for the blue-grey expanse of water, gliding southwards like a giant conveyor-belt.

"Impressed, Max?" asks John.

"Definitely."

I am here, in part, on a literary pilgrimage, hoping to reconnect with the world of Huckleberry Finn, one of my all-time favourite novels. The book is not as popular in the States as it was: the all-pervasive N-word, though quite natural in the mouth of a 19th-century white boy in the American South, does not play well with the PC lobby. On top of which, Huck Finn smokes a pipe. Big no-no in the 21st-century US. But its portrait of one of the world's great rivers exerts a timeless charm.

Twain, born Samuel Langhorne Clemens in Hannibal, Missouri in 1835, was brought up near a steamship landing. As a young man, he worked as a river-boat pilot, committing every bend, sand-bar and swirling eddy to memory.

The Mississippi Delta, the area in which we are camping, inspired some of his most evocative writing. Here is Huck, drifting downriver on a raft with Jim, a runaway slave: "The days just slid along so quiet and smooth and lovely... It was a monstrous big river down there... Not a sound anywheres, perfectly still, just like the whole world was asleep... And we would watch the lonesomeness of the river, and kind of lazy along, and by-and-by lazy off to sleep."

Somnolence is the keynote of the delta and, to some extent, the blues music it inspired. Farther north, the Mississippi pulses with life: bustling towns such as St Louis, Missouri and Memphis, Tennessee. Further south is New Orleans, still reeling from Hurricane Katrina. But here in the delta it is another matter. The Mississippi used to flood so often, and the flood-plain extend so far, that until proper levees were constructed in the 1920s it was madness to build anywhere near the river. Hence the wilderness. Hence the loneliness. Hence the blues.

"There isn't a bridge across the Mississippi between Memphis and Greenville," says John, with a note of pride. "That's nearly 100 miles. Around here, there isn't a building of any description on the river for 40 miles. New Yorkers come and are captivated. They've never seen anything like it." I look across the river, where he is pointing, and see what he means. The sun is high in the sky, bathing the willows in a rich glow. The river is so still it is hard to tell which way it is flowing. Pieces of driftwood dot the virgin sandbanks. Above our heads, a flock of birds flies north in perfect triangular formation.

"Geese?" I ask.

"Pelicans."

John set up the Quapaw Canoe Company in 1998, having come to Mississippi as an outsider - he was born in Colorado - and fallen under the spell of the river. "It has gotten into my soul," he says, with affecting simplicity. Improbably, given the beauty of the surroundings, his company is the only one of its kind, offering canoe-based camping holidays on the river. "A lot of local people are afraid of the Mississippi," he explains. "Some of them can't even swim. There is a whole mythology of shipwrecks and accidents and drowned bodies floating downstream."

As we sit admiring the river, perched on low-slung deckchairs labelled "power loungers" (only in America), we are not totally alone. If there is little by way of leisure craft on the Mississippi, the river remains a major commercial artery. All day, while we are fooling around on our canoe, paddling this way and that, exploring the creeks and the tributaries, having Huck Finn-style adventures, huge tugboats ply the river, ferrying grain, oil, chemicals, scrap metal, cotton, industrial machinery - anything that moves.

The boats are pushing barges that are 250ft long by 30ft wide, and the biggest of them are pushing upwards of 40 barges at a time. They make an extraordinary sight, inching past the sandbanks, and thanks to John's short-wave radio, we are able to catch snatches of the conversations, indelibly Southern in timbre, between the captains of the boats.

"Where yo' goin', dude?" "Natchez. How abou' yo'self?" "St Lou. Then back to Vick. Up an' down, up an' down."

"Hear what happened t' Abe?" "What happened t' Abe?" "Got sucked into the bank five mile back. Bent port rudder. Darn fool. Had to be tugged out. Yo' don' want to get too close to those booeys."

"What are booeys?" I whisper to John. "Booeys is booeys. B-u-o-y." "Oh, you mean buoys. As in 'boys'. The 'u' is silent in England."

"What's the point of it, then?" And there is no arguing with that. As always in America, that old dictum about two countries divided by a common language keeps coming back. Having mislaid my luggage at Newark airport, I am reduced to swimming in my pale blue M&S boxer shorts.

"Your skivvies," says John.

"What's that? Oh, ah, yes. Skivvies."

John, naturally, swims in the buff. He is becoming more like Iron John by the minute. After lunch - beer and turkey sandwiches on the power loungers - he takes us on a route march through the forest, carrying Gavin on his shoulders.

"All you need to watch out for is the poison ivy," says John. "I'll tell you if I see any."

"Yep, mind the ivy," says Gavin cheerfully. "My daddy got some on his willy. He couldn't go wee-wee for..." I march grimly on, cursing Twain and all his works.

But what beauties lie around us, in this magical, untamed wilderness. We see exotically coloured butterflies, a pair of beavers playing on the bank, the pale rump of a deer disappearing into the distance, even the fresh paw-prints of a bear. "Don't see many of them around here," says John, impressed.

It is with real regret that I finally leave Ol' Man River 24 hours later, having paddled 30 miles downstream with John and family. Wesley Jefferson, aka the Mississippi Junebug, is waiting for us with the trailer. He is called the Junebug - a noisy local insect - because he is a part-time blues singer, with a booming baritone that you can hear in Memphis. I get to see him in action that same night, at Ground Zero, a trendy blues bar in Clarksdale, just opposite Madidi, a popular French restaurant co-owned by the actor Morgan Freeman. Junebug is right. Wesley does not just have a big voice, but an expressive one, by turns angry and mournful - pure blues.

Jennifer and Roger Stolle, my companions for the evening, are out-of-staters who have come to live in the delta because they have developed a passion for the region. She teaches English at an all-black secondary school in a run-down part of Clarksdale. He is blues-mad and runs a shop called Cat Head, where you can buy rare blues recordings, as well as folk art from the area.

After Ground Zero, too touristy for his purist tastes, we move on to Red's Lounge, a sleepy, dimly lit joint, where a solitary figure, hunched over his guitar, his eyes half shut, sings of love and loss and days gone by.

There are only half a dozen people listening, drinks in hand; in the background, a young couple are playing pool. But this, for Roger, is the authentic world of the blues - a distinctive musical form, rooted in the delta and in its lonely, isolated communities.

The ghosts of the blues greats - Muddy Waters, Big Jack Johnson, the Jelly Roll Kings - are sounding in my ears as I finally get to bed, in a quirky little hotel called the Shack-Up Inn, another Clarksdale institution.

Guests sleep in rickety wooden shacks and there is an in-house TV channel, on which crackly old LPs are played. You Know What My Body Needs by Smokey Wilson; Strollin' with Bones by T-Bone Walker and his Band. An entire - and splendidly evocative - sub-culture. As I drive out of Clarksdale next morning, Sunday, I pass church after church, every one packed. Some of them sport those jokey slogans so beloved of American pastors. "Exposure to the son may prevent burning." But on the car radio, like a memento of my trip, those Mississippi blues are still throbbing their magic, the words ringing across the cotton fields.

"God knows how I miss you/ All the hell that I've been through... Life throws you the curves/ But you know the swerves..."

Not great verse, perhaps, but redolent of a way of life that is distinctive and fiercely independent. The ghost of Huckleberry Finn lives on.